// Copyright 2006 - Ricardo Stuven (rstuven@gmail.com)
//
// This file is part of MsSqlSpatial.
// MsSqlSpatial is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
// 
// MsSqlSpatial is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public License
// along with MsSqlSpatial; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

using System;
using System.Collections.Generic;
using System.IO;

namespace MsSqlSpatial
{
    /// <summary>
    /// Helper class for aggregate functions.
    /// </summary>
    internal static class Aggregate<T>
    {
        private static readonly Dictionary<string, T> cache = new Dictionary<string, T>();

        public static void Initialize(out string key, out T aggregate)
        {
            key = Guid.NewGuid().ToString();
            if (typeof (T).IsInterface || typeof (T).IsValueType)
            {
                aggregate = default(T);
            }
            else
            {
                aggregate = Activator.CreateInstance<T>();
            }
            cache[key] = aggregate;
        }

        public static T Terminate(string cacheKey)
        {
            T aggregate = cache[cacheKey];
            cache.Remove(cacheKey);
            return aggregate;
        }

        public static void Read(BinaryReader r, out string key, out T aggregate)
        {
            key = r.ReadString();
            aggregate = cache[key];
        }

        public static void Write(BinaryWriter w, string key, T aggregate)
        {
            w.Write(key);
            cache[key] = aggregate;
        }
    }
}